/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements. See the NOTICE file distributed with this
 * work for additional information regarding copyright ownership. The ASF
 * licenses this file to You under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * 
 * http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations under
 * the License.
 */

package org.apache.commons.exec;

/**
 * A default implementation of 'ExecuteResultHandler' used for asynchronous
 * process handling.
 */
public class DefaultExecuteResultHandler implements ExecuteResultHandler {

	/** the interval polling the result */
	private static final int SLEEP_TIME_MS = 50;

	/** Keep track if the process is still running */
	private volatile boolean hasResult;

	/** The exit value of the finished process */
	private volatile int exitValue;

	/** Any offending exception */
	private volatile ExecuteException exception;

	/**
	 * Constructor.
	 */
	public DefaultExecuteResultHandler() {
		this.hasResult = false;
		this.exitValue = Executor.INVALID_EXITVALUE;
	}

	/**
	 * @see org.apache.commons.exec.ExecuteResultHandler#onProcessComplete(int)
	 */
	public void onProcessComplete(int exitValue) {
		this.exitValue = exitValue;
		this.exception = null;
		this.hasResult = true;
	}

	/**
	 * @see org.apache.commons.exec.ExecuteResultHandler#onProcessFailed(org.apache.commons.exec.ExecuteException)
	 */
	public void onProcessFailed(ExecuteException e) {
		this.exitValue = e.getExitValue();
		this.exception = e;
		this.hasResult = true;
	}

	/**
	 * Get the <code>exception<code> causing the process execution to fail.
	 * 
	 * @return Returns the exception.
	 * @throws IllegalStateException
	 *             if the process has not exited yet
	 */
	public ExecuteException getException() {

		if (!hasResult) {
			throw new IllegalStateException(
					"The process has not exited yet therefore no result is available ...");
		}

		return exception;
	}

	/**
	 * Get the <code>exitValue<code> of the process.
	 * 
	 * @return Returns the exitValue.
	 * @throws IllegalStateException
	 *             if the process has not exited yet
	 */
	public int getExitValue() {

		if (!hasResult) {
			throw new IllegalStateException(
					"The process has not exited yet therefore no result is available ...");
		}

		return exitValue;
	}

	/**
	 * Has the process exited and a result is available, i.e. exitCode or
	 * exception?
	 * 
	 * @return true if a result of the execution is available
	 */
	public boolean hasResult() {
		return hasResult;
	}

	/**
	 * Causes the current thread to wait, if necessary, until the process has
	 * terminated. This method returns immediately if the process has already
	 * terminated. If the process has not yet terminated, the calling thread
	 * will be blocked until the process exits.
	 * 
	 * @exception InterruptedException
	 *                if the current thread is {@linkplain Thread#interrupt()
	 *                interrupted} by another thread while it is waiting, then
	 *                the wait is ended and an {@link InterruptedException} is
	 *                thrown.
	 */
	public void waitFor() throws InterruptedException {

		while (!hasResult()) {
			Thread.sleep(SLEEP_TIME_MS);
		}
	}

	/**
	 * Causes the current thread to wait, if necessary, until the process has
	 * terminated. This method returns immediately if the process has already
	 * terminated. If the process has not yet terminated, the calling thread
	 * will be blocked until the process exits.
	 * 
	 * @param timeout
	 *            the maximum time to wait in milliseconds
	 * @exception InterruptedException
	 *                if the current thread is {@linkplain Thread#interrupt()
	 *                interrupted} by another thread while it is waiting, then
	 *                the wait is ended and an {@link InterruptedException} is
	 *                thrown.
	 */
	public void waitFor(long timeout) throws InterruptedException {

		long until = System.currentTimeMillis() + timeout;

		while (!hasResult() && (System.currentTimeMillis() < until)) {
			Thread.sleep(SLEEP_TIME_MS);
		}
	}
}